Distribution. The seedcorn and slender seedcorn beetles are commonly found in the United States in the midwest and northeast, and occur west through the Great Plains and south to South Carolina. In Canada, they are present in eastern provinces, west to at least Ontario. They are native insects. The early accounts of the Stenolophus spp. are unreliable because the species were often confused; despite early reports suggesting that S. lecontei was the most important of the seedcorn beetles, it now appears that S. comma is the most serious pest.
Host Plants. Carabid beetles are known principally as predators of other insects. Animal matter also is the preferred food source of the seedcorn and slender seedcorn beetles. Eggs, larvae, and probably pupae of soil-dwelling insects are readily consumed. For example, Wyman et al. (1976) documented the reduction of cabbage maggot, Delia radicum (Linnaeus), populations when seedcorn beetles were numerous in crucifer plots.
As suggested by the common names, on occasion these beetles will injure germinating seeds, particularly corn seed. However, beetles also feed on weed seeds. Adults of S. comma feed readily on black nightshade, Solanum nigrum; crabgrass, Digitaria sanguinalis; foxtail, Setaria glauca; lambsquarters, Chenopodium album; and purslane, Portulaca oleraceae, and to a lesser degree on other seeds (Pausch, 1979).
Natural Enemies. The natural enemies of these insects are poorly known. The mite Ovacarus clivinae
(Stannard and Vaishampayan) develops inside slender seedcorn beetle, where it is associated with the reproductive system (Stannard and Vaishampayan, 1971).
Life Cycle and Description. These beetles are quite similar in biology. Adults overwinter and can be found throughout the year. Maximum above-ground activity in South Dakota was observed to occur during early summer, followed by almost total absence in late summer, and then reappearance in the autumn. Eggs are most abundant in the spring, larvae and then pupae occur in late spring and early summer, and new adults are produced by mid-summer. Only a single generation is produced annually. Development of the insects from egg to adult requires about 50 days.
by the adults during the spring. Oviposition commences within 14-15 days of emergence, and continues for 5-10 weeks.
The biology of Stenolophus comma was described by Kirk (1975); both S. comma and S. lecontei were considered by Pausch (1979). Slender seedcorn beetle was treated by Phillips (1909) and Pausch and Pausch (1980). These species were included in the keys to adult beetles by Downie and Arnett (1996).
Damage to germinating seeds caused by seedcorn beetles occurs principally during cool and wet weather in spring. Rarely is an ungerminated seed attacked. The contents of the seed are often consumed, leaving only the hull or seed coat. The result of attack is often a poor stand, as seedlings attacked in this manner may perish. However, if only a small portion of the seed is consumed, the seedling may recover and grow normally.
The adult populations can be sampled with pitfall and blacklight traps. Rows of corn in which plants are missing should be examined carefully because beetles can often be found in association with the poorly germinating seeds. The populations of seed corn beetles can be controlled by application of insecticides to the seed, or in liquid or granular form to the soil at planting or shortly after planting (Daniels, 1977). Resistance to insecticides is evident in some populations (Sechriest et al., 1971).
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